Monkey malaria parasites, increasingly posing risks to humans have sparked concerns in Southeast Asia’s battle against malaria.
As cases surge due to zoonotic transmission from monkeys to humans, understanding these parasites, particularly Plasmodium Knowlesi, is crucial amidst efforts to control and eliminate malaria in the region.
What is Monkey Malaria?
Plasmodium Knowlesi is a malaria parasite of monkeys of Southeast Asia that is transmitted by mosquitoes of the Anopheles Leucosphyrus group.
It was discovered in a long-tailed macaque from Singapore in 1931. Although simian malarias were known to be capable of experimentally infecting humans, questions remained about their zoonotic potential.
In 1965, the first natural infection of a human by simian malaria (P. knowlesi) occurred in Malaysia, discovered when a US Army Map Service surveyor fell ill in the jungle.
Prior experiments with humans and rhesus macaques had shown the parasite’s ability to cause severe disease. This discovery highlighted the zoonotic potential of P. knowlesi and led to extensive research in Malaysia’s jungles.
Decades later, misdiagnosed cases in Malaysian Borneo revealed a broader distribution of P. knowlesi infections across Southeast Asia, particularly in northern Borneo. Many cases have been identified passively, prompting questions about the disease’s true prevalence in endemic areas.
Where Monkey Malaria can be found
There are several species of malaria parasites belonging to the genus Plasmodium, four of which infect humans and are transmitted through mosquitoes. Plasmodium falciparum is the deadliest, responsible for most malaria-related deaths in Africa. In other regions, the predominant human-infecting species include P. vivax, P. malariae, and P. ovale.
Human infections with P. knowlesi, previously only found in macaque monkeys, were first identified in Sarawak, Malaysian Borneo, Southeast Asia. Since then, cases of P. knowlesi in humans have increased, with the parasite now detected across most Southeast Asian countries. In Malaysia, it has become the most common form of malaria.
Malaysia experienced extensive forest loss between 2000 and 2012, primarily due to the expansion of oil palm and other tropical crops. This rapid environmental change is believed to have altered the dynamics between macaque monkeys – the natural hosts of P. knowlesi – mosquitoes, and humans. These changes likely facilitated the transmission of the parasite from macaques to humans, illustrating a phenomenon known as disease ‘spillover’.
Symptoms of Monkey Malaria
At least 10% of people infected with P. knowlesi develop severe malaria. Severe P. knowlesi malaria resembles severe malaria caused by P. falciparum. Those with severe disease may experience shortness of breath, abdominal pain, and vomiting.
As disease progresses, parasites replicate to very high levels in the blood likely causing acute kidney injury, jaundice, shock, and respiratory distress.
Metabolic acidosis is uncommon but can occur in particularly severe cases. Unlike P. falciparum malaria, severe P. knowlesi malaria rarely causes coma or severe anemia. Approximately 1-2% of cases are fatal.
Treatment of Monkey Malaria
A study has claimed that many patients have found their cure in treatment with primaquine and chloroquine (anti-malarial drugs) but one unfortunate case out of ten developed serious complications and two died according to the studies. Consulting a doctor is strongly recommended as negligence can cause death.
Between 2006 and 2008, 150 patients were surveyed in Malaysian Borneo. A clinical study of the blood samples showed that of all the patients infected by plasmodium fever, two third of them were suffering from monkey malaria. A recent study has found that direct blood transfer can also lead to monkey malaria in humans.
Can Monkey Malaria cause death?
Since monkey malaria is not original to humans and originally finds its roots in monkeys, its quick diagnosis and treatment are very crucial. A group of researchers in Malaysia has found that if P.K. remains unnoticed and untreated, it can be fatal. The parasite reproduces in the bloodstream every 24 hours, thus making its early treatment highly important.
Is Monkey Malaria endemic yet?
While it is said that monkey malaria isn’t endemic yet, of particular concern to the World Health Orgnisation (WHO) is whether monkey malaria will adapt to better spread between people, which would allow the parasite to thrive in areas without macaques.
While modelling studies have suggested this is not currently happening on a large scale, it’s far from out of the question; a study in 1967 showed it was possible in a controlled setting.
“In my point of view, the question is if/when sustainable human-mosquito-human transmission will be established,” says Dr Elkhan Gasimov, head of the malaria elimination unit at the WHO”It is difficult to predict when exactly this will happen.”
In the meantime, there are signs that other species of zoonotic malaria could follow Plasmodium knowlesi’s lead.
“We’re starting to see spillover in South America as well, with two species: Plasmodium brasilianum and Plasmodium simium,” says Dr Stephen Woolley, an honorary clinical researcher and malaria specialist at the Liverpool School of Tropical Medicine.
“They’re spreading where urban conurbations have expanded into the jungle.
“The monkeys have got nowhere else to go. And therefore humans then get caught in the crossfire.”
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